Discover whether the Diono Rainier 3-in-1 car seat is a good choice for your family in our 2019 review

Diono Rainier 3-in-1 - Review & Verdict

The Diono Rainier is a newly updated version of the high quality brand that is known for excellent safety ratings. It’s one of the few convertible seats (only 8 in the US) that allow for rear-facing children up to 50 pounds. This model is no longer available in stores and their current model is the excellent Radian.

An impressive seat in and of itself, the Diono Rainier has a narrow profile and wide weight range, but it can be a considerable financial investment. Whether or not it’s worth its weight in terms of price is up to you. But we’ve broken down the details so you can quickly determine if it will be the best option for your family.

Why the big deal about how long children are in a rear-facing seat?

Diono Rainier rear-facing

Compared to European countries such as Sweden, parents in the US turn their children forward-facing at a much younger age (often 1 year), though car seat experts recommend leaving them rear -facing until at least 2 years of age.

Research has shown that children should remain rear-facing even longer than that. In Sweden, the average age of switching to forward-facing is 4 years old. Sweden also has the lowest child fatality rate in the world.

The advantage of rear-facing lies in the composition of a child’s body. They may look like little adults, but they’re far from it. A child’s head, neck and spine are still growing and more delicate than an adult’s.

In a wreck, a forward-facing child will experience more violent force on the head, neck and spine. In the rear-facing position, the impact is absorbed over the child’s entire back. The head and neck are well-protected while being pushed back against the seat.

With car seats like the Diono Rainier, it’s possible to keep your child in a rear-facing position until their skeletal system is strong enough to handle impacts in a forward-facing seat.

Key features of the Diono Rainier

Steel frame Diono Rainier

As one of the most premium brands on the market, the Diono Rainier delivers in terms of quality features. As a convertible seat, it will last a long time, so investing a bit more could actually save you money in the long run as you won’t have to buy additional seats as your child grows.

Some of the key features:

  • Extended rear-facing up to 50 pounds
  • Booster mode up to 120 pounds
  • Machine washable cover
  • Infant insert with memory foam
  • Low profile for easy in and out
  • Aluminum reinforced, deep sidewalls
  • Folds flat
  • Steel frame
  • 12-height positions on head support
  • SuperLatch system
  • Rear-facing top tether
  • 10-year lifespan
  • Cup holder included

What are the child size limits for the Diono Rainier?

While the minimum weight of this seat is listed as 5 pounds, some parents thought it felt way too big for their small babies. Though the booster mode has a 120 pound weight limit according to the manufacturer, that may be an overestimation.

Depending on the build and comfort preferences of the child, he may feel as though his shoulders are cramped from the deep sidewalls. Since it’s so narrow, it’s also not as padded as it could be, so long car trips could quickly become uncomfortable for your child.

  • 5 – 50 pounds rear-facing weight range
  • 44 inches rear-facing height max
  • 20 – 90 pounds forward-facing weight range
  • 57 inches forward-facing height range
  • 50 – 120 pounds booster seat weight range
  • 40 – 57 inches booster seat height range

Note: Other comparable Diono seats such as the Diono Radian RXT, Radian R120, and the Radian R100 all have similar weight ranges (5 – 120 pounds), with the exception of the Radian R100 with a max weight of 100. In the order listed, each seat also gets less expensive.

How big is the Diono Rainier and will it fit in my vehicle?

Diono Rainier front-facing

This is one of the most narrow profile seats on the market and will usually fit well if you need more than one car seat. But because of its tall profile, it doesn’t leave a lot of room for a front seat passenger when in the rear-facing position. It’s also a hefty seat right at 30 pounds, and though it can be folded and carried like a backpack when traveling, that’s a pretty big load.

For travelers, the narrowness and foldability make it easy to transport, whether driving, using a taxi, Uber or flying.

  • Seat weight – 29.79 pounds
  • Width (widest point) – 18.5 inches
  • Depth (top of seat) – 9.5 inches
  • Height – 24.5 inches
  • Harness positions – from 8 to 16.5 inches

Note: For comparable Diono seats such as the Diono Radian RXT, Radian R120, and the Radian R100, each is about a pound lighter than the others (in the order listed).

How safe is the Diono Rainier?

The Rainier’s steel frame, though heavy, is sturdy and strong. There’s a SafeStop feature which is attached to the upper part of the car seat. It’s meant to allow crash force energy to dissipate through the harness when the seat is in forward-facing mode. The rear-facing tether reduces rebound energy in a crash as well.

Deep, aluminum-reinforced sidewalls lined with energy absorbing (EPS) foam protect against side impact forces. Unlike other Diono seats, the Rainier has deep side walls, also lined with EPS foam, which provides an additional layer of side impact protection.

The LATCH connectors must be disconnected when your child reaches 35 pounds, which is pretty common to all car seats. But you should have no trouble with seat belt installation alone. The seat also can be installed with the new inflatable seat belts found in some Lincoln and Ford vehicles.

It’s also been proven safe in this account of a real-life crash. Bottom line, if installed properly, you can be fairly certain the seat will be very safe.

How easy is the Diono Rainier to install?

If this seat has one major flaw, it’s installation. Several people had difficulty installing this seat. The instruction manual is vague in some areas, plus there are a lot of steps, which means more chance of bad installation. The SuperLatch system does hold well once installed correctly and has an audible click and visual indicator so you know when it’s locked in place. But getting it installed properly is the hard part.

Besides being heavy, the belt path for rear-facing installation is very narrow and closed so threading the seat belt or LATCH belt through it can be difficult. It’s much easier to access when forward-facing.

The seat tends to slip forward in forward-facing mode, which means you’ll have to lower the adjustable bottom and reinstall. There is no built-in lock-off device for seat belt installation. So you need to know how your vehicle belts work as far as locking goes.

As a booster seat, the padding and seat fabric can grab the seat belt if your child leans forward and thus prevent it from fitting tightly enough on your child. Other issues parents had involved crotch straps that were difficult to move, and having to depend on an angle adjuster (sold separately) to correct the rear-facing angle.

Optional accessories

These items can make using this car seat easier and more comfortable on the road.

Diono Radian Angle Adjuster:
The name suggests that this only works for the Radian model, when in fact it works for all Diono car seats. It helps adjust the rear-facing angle, which improves both backseat space and front seat legroom.
Diono Ultra Mat Full-Size seat protector:
Every car seat (and back seat) can benefit from a seat protector to prevent stains from spills and other debris. It also prevents scratches and indentations in your back seat fabric.
Diono Car Seat Travel Bag:
For toting the seat through an airport or elsewhere, this will come in very handy. It even has a backpack option, is waterproof and has a zippered pocket to store stuff.

Best Car Seat Hub’s Final Verdict

  • Allows extended rear-facing
  • Good weight limits in each mode
  • Narrow profile fits well with other car seats
  • Deep head wings
  • Good leg room
  • Folds flat
  • Rear-facing tether
  • 12-position headrest
  • Heavy
  • Narrow, hard to adjust belt path
  • Crotch positions hard to move
  • Hard to install in some vehicles
  • Seat belt can some loose in booster mode when it catches on the belt positioner
  • No built-in lock-off
  • Pricey
  • Made in China
  • Vague directions with too many installation steps

Final thoughts

For a safe convertible car seat, the Diono Rainier is hard to beat. Sturdy design and solid safety features, plus the extended rear-facing weight range provides more protection, longer than most car seats. It is a significant investment price-wise, but will last a long while with its 3 modes.

If you need to move seats around a lot from car to car, this is not the best option for you. Sure, the fold flat feature is nice for transporting. But the heavy weight, size and difficult installation may lead to more frustration than its worth. It is a good seat if you need multiple car seats in the back seat with its narrow profile, but in some vehicles, your front seat passenger will have very little legroom with this seat in rear-facing mode.

Keep in mind that the upper size limit of 120 pounds may be an exaggeration, depending on your child’s size and comfort levels. Plus, the seat may be a bit too large for very small babies.

All in all, the Diono Rainier is a hefty but solid investment if you don’t need to move the seat around a lot.

Check Diono Rainier Price

This post is also available in: Español (Spanish)


  1. C McKenna says:

    The customer service HAS BEEN TERRIBLE!
    They DON’T answer the phone or return messages.
    Send you things that you don’t want and when you try to return items they don’t refund the total due to the stuff they sent that you DIDN’T want.
    They didn’t send the return label promptly and only gave 48 hours to return the item and then they didn’t send the return label.

  2. Good review. I appreciate to mention both pros and cons. It makes a better understanding about purchasing a product. I have a query only. Will this seat fit in the Odyssey?

    1. Matt Thacker says:

      Yes, this car seat will fit nicely in the second row of the Honda Odyssey.

  3. Rebecca says:

    I personally have purchased 5 Diono carseats, 2 pacificas, 2 r100, and 1 rxt. I LOVE them. They all pretty much stay in the vehicles they are in. The only dislike I have is the the adjustable headpiece of the RXT style. It was fine until my son was about 2 and then he started to find it annoying since he was on the taller side. But, problem solved, we gave it to my niece and upgraded my son to a Pacifica. They have changed model names now, but we have had most every level of their carseat that is full adjustable from infant to booster. I agree with Steve that I do not find installation to be any more difficult than most carseats. Once it is forward facing there is velcro on each side of the seat cover to allow for more pace when using the seatbelt to install. Also, I have never had an issue using the seatbelt in booster mode when we adjusted it for my nephew to use when they were back in the states for a month. Overall, I love these carseats and they are a great long term investment. My son will be six this year and he will still get plenty of use out of this carseat!

    1. Emma Lachey says:

      Hi Rebecca, thanks for your comment. We’re so happy you have had great experiences with Diono line of seats. We hope to review even more of them in the future.

    2. Maria says:

      Hope you saw recall on Pacifica 2 r and other

    3. Matt Thacker says:

      Editor Note: The recall on Diono impacted car seats built from Jan 2014 to Sept 2017 and involved using the lap belt without the top tether. This was a voluntary recall by the manufacturer and no injuries were reported. Models from Diono built after Sept 2017 include an energy absorbing pad and a new chest clip to help mitigate any danger.

  4. Steve says:

    I own 2 of these, so from first hand experience I think this is a fairly good review overall. interesting that you feel the installation is difficult with vague directions, i thought it was pretty straight forward or on par with most other seats (we have many seats in our cars and even in my mom’s car). Perhaps the weight of it makes it SEEM more difficult? Also I’m not sure why made in China is a Con, pretty much all of car seats are made in China, and this appears to be a very high quality seat that stood the test of time for us. Unless you mean this is foreign made and it’s a con for patriotic reasons, which I agree, but then it still doesn’t make sense to single out china unless there’s some personal bias?

    1. Emma Lachey says:

      Hi Steve, thanks for your comment. We’re glad you have had good experiences with this seat, as several other parents have as well. However, one of the biggest challenges parents had was with installation, so that is why we noted that in the review.

      We have no personal bias against any country of origin. However, we’ve noticed more quality control issues, many times due to shipping damage, from seats from China as opposed to other countries.

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